The present invention relates to a self-orienting twin castor with braking assembly.
The “twin” castor is constituted by a pair of wheels which are rotatably mounted on a common axle. The axle is accommodated within a support which comprises a vertical wall which extends between the wheels and is midway between a sort of fairing that covers the castor above: the support is specifically provided with a true hub for the accommodation of the shaft. In the vertical part a well is provided which is open upward and rotatably supports a vertical auto-orientation pin. The hub is adapted to define an engagement seat for an axial shank of the wheels; such seat is generally coaxial to the hole in which the shaft of the wheels is engaged.
The shank is retained in the respective seat (so as to prevent its accidental egress during use) by the interference of an annular portion of the hub: in the insertion step of the wheel an abutment thereof and a part of the annular portion undergo an elastic deformation until the annular portion is overcome by the abutment; naturally the abutting of the abutment on the annular portion, in the operating configuration of the castor, makes an accidental egress impossible.
In this type of castor the braking assembly, which is provided in the hub of the central support, comprises elastic means that are adapted to keep the shaft on which the wheels are mounted resting on respective abutments which protrude inside the hub.
The twin castors are constituted by a pair of wheels mounted on the same shaft, which is rotatably inserted in the support.
Various braking systems are in use which operate outside the hub of the central support. In the specific case of those types which operate inside the hub, a number of systems are known. For example, twin castors comprising the respective braking assemblies on both wheels: in particular, these can have two teeth which are partly integrated in the hub of the support. These teeth provide a cylindrical braking contact surface that interacts with the inner diameter of the wheels (or rollers or disks) so as to provide two braking jaws.
The apparatuses that produce the supports made with such braking assemblies are very expensive and complex, since they must necessarily have molding trolleys for these teeth in the molding apparatuses. In addition to this, the presence of the teeth that support the braking jaws complicates the steps of assembly, since the larger inner diameter of the wheels (or rollers or disks) must necessarily exceed the diameter of the braking jaw (which is smaller than the wheels) before being positioned in its seat.
In this manner the assembly time is delayed. Another system is that which uses a single, centrally-supported slider, which is arranged vertically with respect to the rotation axis. This system, owing to the position in which it is arranged, sometimes does not exert a constant braking action because possible oily residues can be deposited thereon by gravity.